1. Field of the Invention
The present invention relates generally to the data processing field and, more particularly, to a computer implemented method, system, and computer program product for optimizing cache generation for image tiling in GIS/CAD browser applications.
2. Description of the Related Art
A geographic information system (GIS) is a system for capturing, storing, analyzing, and managing data and associated attributes which are spatially referenced to the Earth. In a more generic sense, a geographic information system is a tool that accepts interactive searches, analyzes the spatial information, edits data, maps, and presents the results of all these operations to a user. Geographic information system technology can be used for scientific investigations, resource management, asset management, environmental impact assessment, urban planning, cartography, marketing, and logistics.
A geographic information system may also be web based, meaning that a user can access the geographic information system over the internet through the use of an internet browser. An example of a web based geographic information system is Google Map™. Google Map™ is a trademark of Google Inc.
One of the common techniques used by web based geographic information systems is to pre-generate two dimensional raster images from vector data prior to serving an image to a client. Because the size associated with an image is significantly large, an image is broken into smaller sections prior to serving the image. The smaller sections are also referred to as tiles. When a client requests an area of the image/map, the required tiles are calculated by the server and returned to the client. Additionally, clients may request a larger area as compared to the area currently being displayed on the internet browser. The larger area may be requested to achieve a seamless panning experience to the user.
Currently, due to memory limitations on the client side and the desire to optimize download time, an optimal physical dimension for an image is estimated before receiving a client request. Tiles of equal physical dimensions are generated using the estimated optimal physical dimension. The tiles are then stored on a server associated with the web based geographic information system. When a client requests an image, the tiles are downloaded and assembled on the client system to form the image.
The term optimal, as reference herein, is a condition in which the cache provides a maximum area of an image while maintaining a seamless panning experience to the user. A seamless panning experience is conditioned on the download rate and the screen refresh rate associated with an image.
Computer aided design (CAD) systems are tools used to design, develop and optimize products. Computer aided design systems may also be web based. Although, web based computer aided design systems are less popular than web based geographic information systems due to the significant amount of data involved, computer aided design systems also divide images into fixed tile sizes based on the physical dimensions of the image.
However, fixed tile sizes based on the physical dimension of the image do not provide optimal performance in terms of both download rate and screen refresh rate. Fixed tile sizes (by physical dimensions) vary greatly in memory size making some tiles large and some tiles small in memory. Tile sizes that are too small in memory require a higher rate of screen updates and more requests to the server. Therefore, more overhead is associated with each request. Tile sizes that are too large in memory require longer download times and a slower rate of screen updates resulting in a noticeable lag in updating the tiles.
Accordingly, it would be advantageous to have a computer implemented method, apparatus, and computer program product for modifying tile images in a manner that overcomes the problems described above.